This invention relates to a piezo-electric device such as a piezo bimorph device or a piezo unimorph device functioning as a vibration source in a parts feeder.
A conventional piezo bimorph device includes an intermediate plate and two piezo ceramic elements fixed to both opposite surfaces of the intermediate plate in a sandwich manner. When a voltage is applied to the piezo ceramic elements, the piezo bimorph device bends or vibrates. Thus, the piezo bimorph device is used as a vibration source.
In the past, such a conventional intermediate plate is made of brass, phosphor bronze, stainless steel or spring steel.
The piezo bimorph device including such a conventional intermediate plate has such defects that, if it is used as a vibration source for a parts feeder, the transfer speed is largely affected by the weight of the parts to be transferred and a high voltage must be applied to the piezo bimorph device in order to obtain a desired transfer speed of 5 m/min or more.